Yeah, I think what varies is not so much the tuner, but the ammo due to temperature variation and impact on burn rate and velocity
and on burn rate in one lot of powder to the next, and which primer is used this batch vs. last, and how consistent the loading practices are and what weight of charge actually went into the ammo, case by case.
Then did the tuner setting stay locked?
Are all the screws in the rifle stock tight to the frame? Did the scope get knocked around?
I think there are just as many variables other than the tuner that have to stay the same.